1. Field of the Invention
The present invention pertains to a thermal isolation arrangement for use in scroll fluid devices. The thermal isolation arrangement includes various elements associated with a scroll fluid compressor device and which may be used individually or collectively to thermally isolate cooler inlet fluid to be compressed from hot compressed fluid or hot lubricant in order to increase the efficiency of the scroll compressor.
2. Related Background Technology and Art
Any mechanical device rotating at high speeds generates a considerable amount of thermal energy due to frictional and other effects within the device. High speed mechanical equipment contained within a housing with a driving motor is particularly susceptible to exposure to high temperatures within the device if adequate cooling or heat exchange apparatus is not provided. In sealed refrigeration units enclosing a driving motor and a refrigerant compressor within a sealed housing, heat gain within the housing is produced by the driving motor, the associated bearings, heating of the refrigerant as it is compressed and similar sources. Since the refrigerant is circulating through the sealed unit, a considerable amount of the heat may be extracted from the interior of the sealed housing into the flowing refrigerant and a simple heat exchanger can be associated with the housing to reduce excessive temperatures within the housing that could produce destructive effects.
However, in some instances the cooling effect of the refrigerant is insufficient to achieve sufficient temperature modulation within the housing or is insufficient to avoid loss of efficiency due to heating of the incoming refrigerant on the lower pressure side of the compressor. In some instances, avoiding heating of the inlet refrigerant becomes a significant consideration when the total efficiency of the compressor must be maximized. Thus, while the internal structure of the compressor and motor may be quite capable of withstanding the operating temperature of the sealed refrigeration unit, nevertheless unless some means are taken to avoid transferring the internal heat to the incoming refrigerant, maximum efficiency of the refrigeration unit will not be realized.
This problem has been observed in scroll fluid devices used as refrigerant compressors in a compressor-evaporator system operating at high speed within a sealed housing that encloses a driving motor and associated driving and synchronizing elements for the scroll devices. Such scroll fluid devices include support plates that may be driven in co-rotation about parallel, offset axes to generate progressively and periodically varying fluid transport chambers between axially extending wrap surfaces between the scroll elements when the scroll fluid device is driven so that the axes of symmetry of the scroll elements orbit relative to each other without relative rotation between the scroll wrap surfaces. Such scroll devices normally require a fluid lubricant that becomes heated during operation of the device due to frictional and gas compression effects as well as thermal transfer from the drive motor. Unless precautions are taken, the temperature buildup within the housing is transferred to the incoming refrigerant fluid by conduction and by mixing of the heated lubricating fluid with the incoming refrigerant.
It has become apparent that it is highly desirable in such a scroll fluid device to reduce losses associated with heat transfer between heated components of the scroll device and the fluid being compressed to achieve maximum efficiency for the system. Various heat-insulating arrangements have been proposed to improve the efficiency of scroll fluid devices acting as compressors as represented by Japanese patent publication Nos. 57-206,786 and 62-265,487. In both of these arrangements, a scroll housing is separated into a low pressure chamber, where the intake is located, and a high pressure chamber where the discharge is located. Both of these arrangements utilize a layer of insulating material between these chambers in order to minimize the heat transfer therebetween. In the '786 publication, this heat insulating material extends into an intake chamber formed between the fixed and orbiting scroll members as well as a layer of insulation atop the fixed scroll. Although both of these heat insulating arrangements function to minimize some heat transfer between the discharge fluid and the intake fluid by minimizing the heat transfer through the fixed scroll plate, these arrangements do not prevent or minimize the heat transfer between a rotating support structure for the scrolls nor are they concerned with lubricant mixture with inlet fluid.
Therefore, a need exists for a thermal isolation arrangement for use in a sealed scroll refrigerant compressor fluid device which will not only minimize the heat transfer between the discharge fluid and the intake fluid but also between the internal parts of the scroll fluid device and the intake fluid, and between the lubricant and the intake fluid.